The present invention is directed to an apparatus and method for generating a character pattern signal, and in particular, to an apparatus and method which generates the character pattern signal utilizing a dot pattern formed from outline font data which are stored as bits of outline information.
In present word processors and the like, in order to enhance print quality of a character pattern, the number of dots which form the character pattern need to be increased. However, this requires a corresponding increase in storage capacity of the character generator because of the need for storing additional dot pattern data for each character. The conventional manner for obviating this problem has been through the introduction of an outline system. As shown in FIG. 6 of the drawings, in the outline system, the outline of a character pattern is divided into a plurality of regions extending about the perimeter of a character such as regions J.sub.0, J.sub.1, J.sub.2. The coordinates of an initial starting point and a terminal point for each region J.sub.0, J.sub.1, J.sub.2 are stored as data and the section of the outline between these points is compensated by dot signals during the outputting of the signal. With this system, it becomes possible to output high quality characters utilizing a large number of dots while reducing the amount of data which is required to be stored as well as providing the capability of enlarging and shrinking the size of the character by effecting coordinate arithmetic operations allowing the character to be produced in a variety of character sizes.
As seen in FIG. 7A, an approximation of a curve perimeter J.sub.n forming a character outline typically includes two straight lines K as shown in FIG. 7B joining a circular arc L at respective points Q. Therefore, when precisely approximating a curve or linear portion of an outline section J.sub.n, it is necessary to store a large number of representative circular arcs having different radii thus increasing the storage capacity required in the conventional system.
To eliminate the need for increased storage capacity a method illustrated in FIG. 7C has been utilized in which the curve is identified by the data equivalent of a conic spline which defines a curve having three points, the initial point A and a terminal point B both of which are on the actual curve to be defined and a control point C which is formed at an intersection of a tangent line extending from the curve at initial point A and terminal point B. [The conic spline functions to provide an approximation of a character outline by the use of a smooth curve while requiring a small storage capacity. However, the use of the mathematical conic spline does require complicated arithmetic operations requiring a sufficiently increased real time until the dot signals are output.
It is desired to present an apparatus and method for generating character pattern signals which overcome the shortcomings of the prior art by defining a character without the need for a large storage capacity or complicated arithmetic operations.